Use of crude glycerol (cg) for production of formulations for mineral oil production and process for producing mineral oil from mineral oil deposits having inhomogeneous permeability

ABSTRACT

The present invention relates to the use of crude glycerol (CG) as a constituent of a formulation for mineral oil production and to a process for producing mineral oil from mineral oil deposits having inhomogeneous permeability. The inventive use of crude glycerol (CG) makes it possible to modify the rheological properties of the inventive formulations (F) within wide ranges, and makes it possible to adjust them to the geotechnical parameters, the environmental conditions and the nature of the mineral oil in different mineral oil deposits.

This patent application claims the benefit of pending U.S. provisionalpatent application Ser. No. 61/667,962 filed on Jul. 4, 2012,incorporated in its entirety herein by reference.

The present invention relates to a process for producing mineral oilfrom mineral oil deposits having inhomogeneous permeability. Theinventive use of crude glycerol (CG) makes it possible to modify therheological properties of the inventive formulations (F) within wideranges, and makes it possible to adjust them to the geotechnicalparameters, the environmental conditions and the nature of the mineraloil in different mineral oil deposits.

In natural mineral oil deposits, mineral oil occurs in cavities ofporous reservoir rocks which are closed off from the surface of theearth by impervious overlying strata. In addition to mineral oil,including proportions of natural gas, a deposit further comprises waterwith a higher or lower salt content. The cavities may be very finecavities, capillaries, pores or the like, for example those having adiameter of only approx. 1 μm; the formation may additionally also haveregions with pores of greater diameter and/or natural fractures,however. In a mineral oil deposit, one or more oil-bearing strata may bepresent.

After the well has been sunk into the oil-bearing strata, the oil atfirst flows to the production wells owing to the natural depositpressure, and erupts from the surface of the earth. This phase ofmineral oil production is referred to by the person skilled in the artas primary production. In the case of poor deposit conditions, forexample a high oil viscosity, rapidly declining deposit pressure or highflow resistances in the oil-bearing strata, eruptive production rapidlyceases. With primary production, it is possible on average to produceonly 2 to 10% of the oil originally present in the deposit.

Mineral oil production is differentiated into primary, secondary andtertiary production.

In order to enhance the yield, what are known as secondary productionprocesses are therefore used. The most commonly used process insecondary mineral oil production is water flooding. This involvesinjecting water through injection wells into the oil-bearing strata.This artificially increases the deposit pressure and forces the oil outof the injection wells to the production wells. By water flooding, it ispossible to substantially increase the yield level under particularconditions.

It is additionally possible to increase the mineral oil yield further bymeasures of tertiary oil production. In tertiary oil production,suitable chemicals are used as assistants for oil production. Thisincludes what is called “polymer flooding”. Polymer flooding involvesinjecting an aqueous solution of a thickening polymer into the mineraloil deposit through the injection wells instead of water. These aqueoussolutions are also referred to as flooding compositions for tertiarymineral oil production. As a result of the injection of the polymersolution, the mineral oil is forced through said cavities in theformation from the injection well proceeding in the direction of theproduction well, and the mineral oil is finally produced through theproduction well. Due to the elevated viscosity of the polymer solution,which is matched to the viscosity of the mineral oil, the polymersolution is thus able to break through cavities at least not as easilyas is the case for pure water, if at all. Parts of the deposit notaccessible to the water are reached by the polymer solution.

The flooding compositions used for tertiary mineral oil production areaqueous solutions of a multitude of different thickening water-solublepolymers, both synthetic polymers, for example polyacrylamide orcopolymers of acrylamide and other monomers, especially monomers havingsulfo groups, and polymers of natural origin, for exampleglucosylglucans, xanthans or diutans.

The above-described polymers, however, are costly, and so the usethereof as a constituent of a flooding composition in tertiaryproduction processes leads to a significant increase in cost of themineral oil produced.

In the ideal case of water flooding, a water front proceeding from theinjection well should force the oil homogeneously over the entiremineral oil formation to the production well. In practice, a mineral oilformation, however, has regions with different levels of flowresistance. In addition to oil-saturated reservoir rocks which have fineporosity and a high flow resistance for water, there also exist regionswith low flow resistance for water, for example natural or syntheticfractures or very permeable regions in the reservoir rock. Suchpermeable regions may also be regions from which oil has already beenrecovered. In the course of water flooding, the flooding water injectednaturally flows principally through flow paths with low flow resistancefrom the injection well to the production well. The consequences of thisare that the oil-saturated deposit regions with fine porosity and highflow resistance are no longer flooded, and that increasingly more waterand less mineral oil is produced via the production well. In thiscontext, the person skilled in the art refers to “watering out ofproduction”. The effects mentioned are particularly marked in the caseof viscous mineral oils.

For production of mineral oil from deposits with high mineral oilviscosity, the mineral oil can also be heated by injecting steam in thedeposit, thus reducing the oil viscosity. As in the case of waterflooding, however, steam and steam condensate can also strikeundesirably rapidly through high-permeability zones from the injectionwells to the production wells, as a result of which the efficiency ofthe production is reduced.

It is customary at present to conduct both steps when developingdeposits containing viscous oil: water flooding followed by steamflooding.

The prior art discloses measures for closing such high-permeabilityzones between injection wells and production wells by means of suitablemeasures. As a result of these, high-permeability zones with low flowresistance are blocked and the flooding water or the flooding steamflows again through the oil-saturated, low-permeability strata. Suchmeasures are also known as “conformance control”. An overview ofmeasures for conformance control is given by Borling et al. “Pushing outthe oil with Conformance Control” in Oilfield Review (1994), pages 44ff.

For conformance control, it is possible to use comparativelylow-viscosity formulations of particular chemical substances which canbe injected easily into the formation, and the viscosity of which risessignificantly only after injection into the formation under theconditions which exist in the formation. To enhance the viscosity, suchformulations comprise suitable inorganic, organic or polymericcomponents. The rise in viscosity of the injected formulation canfirstly occur with a simple time delay. However, there are also knownformulations in which the rise in viscosity is triggered essentially bythe temperature rise when the injected formulation is gradually heatedto the deposit temperature in the deposit. Formulations whose viscosityrises only under formation conditions are known, for example, as“thermogels” or “delayed gelling systems”. However, these formulationscan be employed efficiently only in deposits whose temperature is above60° C.

SU 1 654 554 A1 discloses processes for producing oil, in which mixturescomprising aluminum chloride or aluminum nitrate, urea and water areinjected into the mineral oil formations. At the elevated temperaturesin the formation, the urea is hydrolyzed to carbon dioxide and ammonia.The ammonia which forms significantly increases the pH of the water, asa result of which high-viscosity aluminum hydroxide gel precipitatesout, which blocks the high-permeability regions.

RU 2 339 803 C2 describes a process for blocking high-permeabilityregions in mineral oil deposits, in which the volume of thehigh-permeability region to be blocked is first of all determined.Subsequently, an aqueous formulation comprising carboxymethylcelluloseand chromium acetate as a crosslinker is injected into the region to beblocked, the volume of the injected mixture being 15%, based on thetotal volume of the region to be blocked. In the next step, an aqueousformulation comprising polyacrylamide and a crosslinker is injected.

L. K. Altunina and V. A. Kushinov, Oil & Gas Science and Technology—Rev.IFP, Vol. 63 (2008), pages 37 to 48 and Altunina L. K., Kuvshinov V. A.,Stasyeva L. A.//Thermoreversible Polymer Gels for Increased Efficiencyof Cyclic-Steam Well Treatment,—2006—1 CD-ROM,—68th EAGE Conference &Exhibition “Opportunities in Marine Areas”, Paper D030 describe variousthermogels and the use thereof for oil production, including thermogelsbased on urea and aluminum salt, and thermogels based on celluloseethers.

The above-described gel-forming formulations are “thermogels”, i.e.formulations whose viscosity rises with increasing temperature. Adisadvantage of these thermogels is that they can be used only inmineral oil deposits which have deposit temperatures of at least 60° C.

It was therefore an object of the present invention to provide aformulation for production of mineral oil which has the above-describeddisadvantages of the prior art only to a reduced degree, if at all. Theformulation is to be suitable for blocking of highly permeable zones inmineral oil deposits having deposit temperatures below 60° C. Theformulation is additionally to be suitable as a flooding composition fortertiary mineral oil production. The rheological and physical parametersof the formulation are to be modifiable within wide ranges and to allowefficient profile modification of the flood front.

It was a further object of the present invention to provide a processfor producing mineral oil from mineral oil deposits having inhomogeneouspermeability using these formulations.

This object is achieved by the process for tertiary production ofmineral oil from underground mineral oil deposits having a deposittemperature T_(D), into which at least one injection well and at leastone production well have been sunk, comprising at least the followingprocess steps:

i) injecting a flooding composition through at least one injection wellinto the mineral oil deposit, using, as the flooding composition, aformulation (F) having a temperature T_(F) higher than the temperatureT_(D),

ii) cooling the flooding composition from step i) in the mineral oildeposit and

iii) injecting a further flooding composition through at least oneinjection well into the mineral oil deposit and withdrawing mineral oilthrough at least one production well, wherein the formulation (F)comprises crude glycerol (CG) has the following composition:

-   -   80 to 90% by weight of glycerol,    -   10 to 20% by weight of water,    -   0 to 10% by weight of inorganic salts and    -   0 to 1% by weight of organic compounds,    -   where the percentages by weight are each based on the total        weight of the crude glycerol (CG).

It has been found that, surprisingly, crude glycerol (CG), which isinexpensive and not of ecological concern, is suitable for production offormulations (F) suitable as flooding compositions for tertiary mineraloil production or as compositions for blocking of highly permeable zonesin mineral oil deposits.

The rheological and physical properties of the formulation (F) can bemodified and adjusted easily by simple variation of the componentconcentrations, especially of the concentration of crude glycerol (CG).

It is thus possible to adjust the formulations (F) in a simple manner tothe geotechnical parameters and environmental conditions, i.e. moreparticularly to the deposit temperature and the viscosity of the oilpresent in the deposit. The inventive formulations (F) are especiallysuitable for use in mineral oil deposits having relatively low deposittemperatures (cold mineral oil deposits). The use of crude glycerol (CG)allows the rheological and physical properties of the formulation (F) tobe varied within wide ranges, such that the formulation (F) can also beused in the development of mineral oil deposits having relatively highdeposit temperatures (hot mineral oil deposits). A further advantage ofthe inventive formulation (F) is that the freezing temperature can alsobe regulated within wide ranges. By varying the component contents,especially the concentration of crude glycerol (CG), it is possible tosignificantly reduce the freezing temperature. This enables the use ofthe formulation (F) in the development of mineral oil deposits in coldregions of the earth too, for example in permafrost regions. The densityof the formulation (F) can be adjusted such that it is greater than thedensity of the deposit water and/or mineral oil which occurs in themineral oil deposit. It is thus possible to enhance the efficiency ofthe oil displacement.

In the context of the present invention, cold mineral oil deposits areunderstood to mean deposits having temperatures<60° C. Hot mineral oildeposits are understood to mean deposits having a temperature of atleast 60° C.

The viscosity of the formulations (F) decreases with rising temperatureand increases with decreasing temperature. In other words, theformulations (F) have a low viscosity at relatively high temperatures,whereas the viscosity of the formulation (F) rises when the temperatureis lowered. The formulation (F) thus differs from the conventionalthermogels described in the prior art, where the viscosity rises whenthe temperature increases. The conventional thermogels have a lowviscosity at low temperatures, whereas the viscosity thereof risessignificantly with increasing temperature.

Glycerol is a trihydric alcohol (IUPAC name 1,2,3-propanetriol) havingthe formula CH₂(OH)—CH(OH)—CH₂(OH). Glycerol is produced bypetrochemical means from propene via the allyl chloride andepichlorohydrin intermediates. Crude glycerol (CG) shall be understoodin the context of the present invention to mean all mixtures comprisingglycerol, water, inorganic salts and organic compounds (other thanglycerol). Preference is given, however, to crude glycerol (CG) which isobtained from natural fats or oils. Glycerol is a constituent of allanimal and vegetable fats/oils. Crude glycerol (CG) is obtained in largeamounts as a by-product of biodiesel production. For production ofbiodiesel, vegetable oils, for example rapeseed oil, are transesterifiedwith methanol. A fat/oil molecule (triacyl glyceride) is reacted withthree methanol molecules to give glycerol and three fatty acid methylesters. Thus, 10 liters of vegetable oil and 1 liter of methanol giveapprox. 10 liters of biodiesel and 1 liter of crude glycerol.

Crude glycerol (CG) preferably has the following composition:

-   -   80 to 90% by weight of glycerol,    -   10 to 20% by weight of water,    -   0 to 10% by weight of inorganic salts and    -   0 to 1% by weight of organic compounds,

where the percentages by weight are each based on the total weight ofthe crude glycerol (CG).

Particular preference is given to crude glycerol (CG) having thefollowing composition:

-   -   80 to 82% by weight of glycerol,    -   10 to 15% by weight of water,    -   5 to 7% by weight of inorganic salts comprising sodium chloride        and    -   0.01 to 0.5% by weight of methanol,

where the percentages by weight are each based on the total weight ofthe crude glycerol (CG).

The inorganic salts are also referred to as ash. Ash constitutes theignition residue of the crude glycerol (CG).

The crude glycerol (CG) may of course comprise further components whichare obtained as impurities in the production of crude glycerol (CG).Preferably, the content of further components in the crude glycerol(CG), however, is below 1% by weight, more preferably below 0.5% byweight and especially below 0.1% by weight, based in each case on thetotal weight of the crude glycerol (CG).

Crude glycerol (CG) at 20° C. has a density of 1.23 to 1.27 g per cm³.The viscosity of crude glycerol (CG) at 20° C. is in the range from 700mPa*s to 1200 mPa*s. The viscosity of the crude glycerol (CG) depends onthe water content and any inorganic salts present in the crude glycerol(CG). The organic compounds present in crude glycerol (CG) arepreferably methanol, especially in concentrations in the range from 0.01to 0.5% by weight, based on the total weight of the crude glycerol (CG).The inorganic salts present are preferably sodium chloride and/orpotassium chloride, especially in concentrations in the range from 5 to7% by weight, based on the total weight of the crude glycerol (CG).Crude glycerol (CG) has the advantage that it is not of toxicologicalconcern and is biodegraded. Crude glycerol (CG) can therefore also beused in ecologically sensitive areas as a constituent of a formulationfor production of mineral oil.

In the last few years, the production of biodiesel, particularly in theEuropean Union, has risen rapidly. The production of crude glycerol (CG)in the European Union has reached a volume of approximately 1 milliontonnes. A viable use for the crude glycerol (CG) obtained in biodieselproduction is a great economic problem which has not been solved todate. The invention enables a viable use of the wastes obtained inbiodiesel production (crude glycerol (CG)). Crude glycerol (CG)additionally has the advantage of being available inexpensively and inlarge volumes.

Use of the Formulation (F) as a Composition for Mineral Oil Production

Particularly suitable formulations (F) are those which comprise at least10% by weight of crude glycerol (CG), based on the total weight of theformulation (F). The invention thus also provides for the use of aformulation (F) comprising at least 10% by weight of crude glycerol(CG), based on the total weight of the formulation, as a composition formineral oil production. In addition, the invention also provides for theuse of an aqueous formulation (F) comprising at least 10% by weight ofcrude glycerol (CG), based on the total weight of the formulation (F),as a composition for mineral oil production.

Additionally particularly suitable are formulations (F) which, as wellas crude glycerol (CG), comprise water. The invention thus also providesfor the use of a formulation (F) comprising 10 to 99% by weight of crudeglycerol (CG), 1 to 90% by weight of water and 0 to 20% by weight of atleast one inorganic salt, where the percentages by weight are each basedon the total weight of the formulation (F), as a composition for mineraloil production.

Preferred inorganic salts are sodium chloride and/or calcium chloride,particular preference being given to calcium chloride.

The viscosity, density, freezing temperature and final viscosity of theformulations (F) can be matched to the geological conditions in themineral oil deposit. If, for example, the deposit water (also calledformation water) has a density (D_(D)), increasing the concentration ofthe crude glycerol (CG) present in the formulation (F) can increase thedensity (D_(F)) of the formulation (F) such that D_(D)<D_(F). Thisachieves effective displacement of the deposit water and ultimately ofthe mineral oil. To further increase the density (D_(F)) of theformulation (F), inorganic salts, preferably sodium chloride and/orcalcium chloride, can be added thereto.

If the mineral oil deposit is within cold regions of the earth and has adeposit temperature (T_(D)) and the outside temperature above ground is(T_(OT)), the freezing temperature (T_(FF)) of the formulation (F) canbe reduced by the increase in the concentration of crude glycerol (CG)such that (T_(D)) is greater than or equal to (T_(FF)). It is alsopossible to reduce the freezing temperature (T_(FF)) such that (T_(OT))is greater than or equal to (T_(FF)). This enables the use of theformulation also in regions where prevalent temperatures above groundare below freezing point, for example in the range from minus 50 to 0°C. This enables the use of the formulation (F) also in permafrostregions.

Freezing temperature is understood to mean the temperature at which theformulation (F) solidifies, i.e. forms a solid.

If the formulation (F) is used as a flooding composition fordisplacement of mineral oil from the mineral oil deposit, the viscosity,the density and the final viscosity of the formulations (F) can bematched to the viscosity and density of the mineral oil in order tooptimize the displacement thereof.

The formulation (F) may further comprise further additives, for examplesurfactants, urea or water-soluble thickening polymers, such ascellulose ethers, glucosylglucans, xanthans or diutans, and syntheticpolymers, such as polyacrylamide, or copolymers of acrylamide withmonomers containing sulfo groups.

However, the formulation (F) preferably comprises not more than 1% byweight, more preferably not more than 0.5% by weight and especially notmore than 0.1% by weight of further additives, based in each case on thetotal weight of the formulation (F).

The percentages by weight of the individual components of theformulation (F) are generally selected such that the sum thereof adds upto 100% by weight. Preference is given to formulations (F) which consistof the above-described components, i.e. crude glycerol (CG), optionallywater, optionally inorganic salts.

The percentages by weight of water and optionally of sodium chlorideand/or calcium chloride in the formulation (F) do not include the amountof the water and any amounts of sodium chloride and/or calcium chloridealready present in the crude glycerol (CG). The percentages by weight ofwater and sodium chloride and/or calcium chloride in the formulation (F)should be understood as additional amounts of water and sodium chlorideand/or calcium chloride. To calculate the total amount of the amount ofwater present in the formulation (F), the amount of water present in thecrude glycerol (CG) and the amount of water additionally added shouldthus be added up. To calculate the total amount of sodium chlorideand/or calcium chloride in the formulation (F), the amounts of sodiumchloride and/or calcium chloride present in the crude glycerol (CG) andthe amounts of sodium chloride and/or calcium chloride additionallyadded should likewise be added up.

In addition, particularly suitable formulations (F) are those whichcomprise at least 80% by weight, preferably at least 90% by weight andmore preferably at least 99% by weight of crude glycerol (CG). Theinvention thus also provides for the use of a formulation (F) whichcomprises at least 80% by weight, preferably at least 90% by weight andmore preferably at least 99% by weight of crude glycerol (CG), where thepercentages by weight are each based on the total weight of theformulation (F), as a composition for mineral oil production.

In addition, particularly suitable formulations (F) are those whichconsist essentially of crude glycerol (CG). This is understood in thepresent context to mean formulations (F) comprising not more than 0.5%by weight and especially not more than 0.1% by weight of furthercomponents other than crude glycerol (CG).

Formulations (F) having concentrations of crude glycerol (CG) of atleast 80% by weight have a growth-inhibiting effect on themicrobiological fauna in the mineral oil deposit. It has been found thatthe growth of microorganisms is accelerated at concentrations of crudeglycerol (CG) in the range from 1 to 25% by weight, preferably in therange from 10 to 25% by weight, of crude glycerol (CG). The presentinvention thus also provides for the use of a formulation (F) comprising10 to 25% by weight of crude glycerol (CG), based on the total weight ofthe formulation (F), as a composition for mineral oil production,especially for acceleration of the growth of microorganisms.

Oil production processes using microorganisms have been described in theprior art as MEOR (microbial enhanced oil recovery) processes. In thecase of the inventive use, the microorganisms can be added to theformulation (F).

It has been found that the inventive formulation (F) can be used as aflooding composition for tertiary mineral oil production. The presentinvention thus also provides for the use of a formulation (F) as aflooding composition for tertiary mineral oil production.

In the case of use of the formulation (F) as a flooding composition fortertiary mineral oil production, preference is given to formulations (F)which comprise, as well as at least 10% by weight of crude glycerol(CG), additionally water and optionally sodium chloride and/or calciumchloride and optionally additional additives, where the above remarksapply correspondingly to the concentrations.

In addition, it has been found that the inventive formulation (F) can beused as a formulation for blocking high-permeability zones in a mineraloil deposit. The present invention thus also provides for the use of aformulation (F) as a composition for blocking high-permeability zones ina mineral oil deposit. In the case of use of the formulation (F) as acomposition for blocking high-permeability zones in a mineral oildeposit, preference is given to formulations (F) having concentrationsof crude glycerol (CG) of at least 80% by weight.

The inventive formulation (F) is advantageously used in mineral oildeposits having temperatures in the range from 0 to 180° C. Particularpreference is given to the use of the formulation (F) in mineral oildeposits having a deposit temperature (T_(D)) below 60° C. Especiallypreferred is the use of the formulation (F) in mineral oil depositshaving a deposit temperature (T_(D)) in the range from 0 to 40° C., morepreferably in the range from 2 to 30° C. The present invention thus alsoprovides for the use of the formulation (F) in a mineral oil deposithaving a deposit temperature below 60° C., preferably in the range from0 to 40° C., more preferably in the range from 2 to 30° C., as acomposition for mineral oil production from mineral oil deposits.

The use of the formulation (F) enables balancing of the profile of theflood front (also referred to as profile modification). The presentinvention thus also provides for the use of the formulation (F) as acomposition for balancing the profile of the flood front in a mineraloil deposit.

The inventive formulation (F) does not form a gel when the temperatureis altered. When the temperature rises, the viscosity of the formulation(F) is lowered; when the temperature is reduced, the viscosity of theformulation (F) rises.

The inventive formulations (F) can be produced by simple processes, forexample by simple mixing of the liquid components, and optionally bydissolution of solid components in the liquid components.

If the formulation (F) comprises water, it is possible to use fullydemineralized water, tapwater, seawater, partially demineralizedseawater or water which has been produced from the mineral oil deposit(called deposit or formation water). If the formulation (F) comprisesinorganic salts, preference is given to using seawater or formationwater.

The viscosity of the undiluted crude glycerol (CG) at a temperature of20° C. is in the range from 700 to 1200 mPa*s and is much higher thanthe viscosity of the flood water which is used in conventional flooding.The viscosity of the formulation (F) depends particularly on theconcentration of crude glycerol (CG) and water. The higher the crudeglycerol (CG) concentration, the higher the viscosity of the formulation(F). Conversely, the viscosity of the formulation (F) decreases withincreasing water concentration, i.e the higher the water concentrationof the formulation (F), the lower the viscosity of the formulation (F).By varying the aforementioned concentrations, it is thus possible toadjust the viscosity of the formulation (F).

A further advantage of the inventive formulation (F) is that theviscosity of the formulation (F) increases with falling temperature. Theviscosity of the formulation (F) can be adjusted such that it is higherby a factor of 10 to 100 than the formation water present in thedeposit. Formation water in the present context is also understood tomean the flooding water which may have been injected in a preceding stepinto the deposit, for example in the course of secondary productionprocesses. As a result of the higher viscosity of the formulation (F),possibly in conjunction with an elevated density, the formation water,which has a much lower viscosity and density, is effectively displaced,as a result of which a profile modification of the flood front andmobilization of mineral oil in stagnation zones are achieved.

The formulation (F) can be injected into the mineral oil deposit inlarge volumetric masses, for example in amounts of 500 to 50 000 m³.

Since the viscosity of the formulation (F) decreases at hightemperatures, it has been found to be advantageous to use theformulation (F) with a temperature (T_(F)) higher than the deposittemperature (T_(D)).

At the temperature (T_(F)), the viscosity of the formulation (F) islower than at the temperature (T_(D)). As a result of this, theformulation (F) can penetrate deep into the mineral oil deposit andfills especially zones therein which have been washed out, i.e. zoneswith high permeability. In the mineral oil deposit, the formulation (F)cools down, as a result of which the viscosity of the formulation (F)rises and the mobility of the formulation (F) decreases significantly.

Crude glycerol (CG) dissolves readily in water, as a result of which theconcentration of crude glycerol (CG) decreases relatively rapidly,especially at the edge and at the flood front. In the core region of thevolumetric zone, the mobility of the formulation (F) is much lower,ideally virtually 0.

Process for Producing Mineral Oil from an Underground Mineral OilDeposit:

The present invention also provides a process for tertiary production ofmineral oil from underground mineral oil deposits having a deposittemperature T_(D), into which at least one injection well and at leastone production well have been sunk, comprising at least the followingprocess steps:

-   -   i) injecting a flooding composition through at least one        injection well into the mineral oil deposit, using, as the        flooding composition, a formulation (F) having a temperature        T_(F) higher than the temperature T_(D),    -   ii) cooling the flooding composition from step i) in the mineral        oil deposit and    -   iii) injecting a further flooding composition through at least        one injection well into the mineral oil deposit and withdrawing        mineral oil through at least one production well.

The process according to the invention for producing mineral oil is aprocess for tertiary mineral oil production, i.e. it is employed afterprimary mineral oil production has stopped due to the autogenouspressure of the deposit and the pressure in the deposit has to bemaintained by injection of water and/or steam (secondary production) orby injection of an aqueous polymer solution (tertiary production).

For the formulations (F) used in the process according to the invention,the remarks and preferences expressed above regarding the use of theformulation (F) apply correspondingly.

The use of the formulation (F) in a process for producing mineral oilfrom an underground mineral oil deposit allows watering-out ofproduction to be reduced and the level of oil recovery from the mineraloil deposit to be enhanced.

The process according to the invention has the advantage that, even indeposits with low temperature, high-permeability zones can be blockedselectively by means of the formulation (F). The process enablesblockage even of washed-out rock zones in the deposit which have beencooled (for example by water flooding). The distance between theborehole (the injection well) and the zone in which the mobility of theformulation (F) decreases due to the viscosity rise can be regulated inthe process according to the invention particularly through the amountof crude glycerol (CG) and the temperature T_(F) with which theformulation (F) is injected into the mineral oil deposit. This achievesefficient blocking of high-permeability zones, reduces watering-out ofproduction and increases the level of oil recovery.

In a preferred embodiment, the process according to the invention isemployed in mineral oil deposits having a deposit temperature T_(D)below 60° C., more preferably in the range from 0 to 40° C. andespecially in the range from 2 to 30° C.

The deposits may be deposits for all kinds of oil, for example those forlight or heavy oil. In one embodiment of the invention, the deposits areheavy oil deposits, i.e. deposits comprising mineral oil having an APIgravity of less than 22.3° API.

The optimal area for the use of the formulation (F) is in what arecalled “mature” deposits comprising oils having moderate or lowviscosity.

The viscosity of the formulation (F) used as the flooding compositiondepends predominantly on the concentration of the crude glycerol (CG)used and on the deposit temperature. It should be matched to theviscosity of the mineral oil present in the mineral oil deposit and canbe determined more accurately with the aid of the ratio (A) between theflooding composition mobility (Mw) and the mineral oil mobility (Mo).

A=Mw/Mo=(krw/μw)/(krw/μo),

krw—relative permeability of the mineral oil deposit for the floodingcomposition,

kro—relative permeability of the mineral oil deposit for mineral oil,

μo—mineral oil viscosity,

μw—viscosity of the flooding composition.

μw relates here to the viscosity of the flooding composition under theconditions in the mineral oil deposit. Ideally, the viscosity of theflooding composition (under the conditions in the mineral oil deposit)is adjusted so as to result in A values of <1. At A<1, the personskilled in the art expects piston-like displacement of the oil. Theoptimal ratio (A) between the flooding composition mobility (Mw) and themineral oil mobility (Mo) is unattainable in some cases particularly forhigh-viscosity oils, since unrealistically high injection pressures haveto be developed. It is therefore also necessary to work with A valuesof >1. However, even a relatively small increase in the viscosity of theflooding composition tends to improve the mineral oil yield.

In the case of optimization of the properties of the floodingcomposition comprising crude glycerol (CG), the viscosity of theflooding composition (μw) entered into the formula A=Mw/Mo is theviscosity after cooling in the deposit (final viscosity). Thepermeability is measured in darcies. The viscosity is measured in mPa*s.

The process according to the invention can be employed as soon asproduction in secondary production processes experiences excessivewatering-out, or what is called a water breakthrough is registered. Thisis generally the case when a mixture comprising more than 70% by weight,particularly more than 90% by weight, of deposit water is withdrawn fromthe production well, based on the total weight of the mixture withdrawnfrom the production well. In the event of a water breakthrough, waterflows through high-permeability zones from the injection well to theproduction well. Highly permeable zones, however, need not necessarilybe obtained as a result of the water flooding, but may also be presentnaturally in a formation. In addition, it is possible that permeablezones have already been created in a process step preceding the processaccording to the invention.

For preparation for the process according to the invention, it may beadvantageous to measure the temperature in the region of the injectionwell and to determine the temperature range of the deposit in the regionunder the influence of flooding. Methods for determining the temperaturerange in a mineral oil deposit are known in principle to those skilledin the art. The temperature distribution is generally undertaken fromtemperature measurements at particular sites in the formation incombination with simulation calculations, and the simulationcalculations take account of factors including amounts of heatintroduced into the formation and the amounts of heat removed from theformation. Alternatively, each of the regions may also be characterizedby the average temperature thereof. It is clear to the person skilled inthe art that the analysis of the temperature range outlined constitutesmerely an approximation of the actual conditions in the formation.

In the course of the process according to the invention, highlypermeable zones of the mineral oil deposit in the region between theinjection wells and the production wells are blocked by injecting theformulation (F) through the at least one injection well.

Process Step i)

According to the invention, at least one formulation (F) is used forthis purpose. It is also possible to successively inject two or moreformulations (F) of different composition.

According to the invention, the formulation (F) is injected into themineral oil deposit through one or more injection wells. The injectionof the formulation (F) may optionally be followed by further waterflooding in order to displace the formulation (F) further into themineral oil deposit. In the context of the present invention, furtherflooding refers to the water volume which is injected directly after theinjection of the formulation (F) in order to bring the formulation (F)to the desired site in the mineral oil deposit underground. However, dueto the low viscosity of the formulation (F), this is not absolutelynecessary. In one embodiment, no further flooding follows process stepi).

To execute the process, at least one production well and at least oneinjection well are sunk in the mineral oil deposits. In general, adeposit is provided with several injection wells and with severalproduction wells.

The deposit temperature can be altered through the use of the processaccording to the invention, typically at least within the region betweenthe injection wells and the production wells.

In process step i), one or more flooding compositions are injectedthrough the at least one injection well into the mineral oil deposit.

Preferably, T_(F), with which the formulation (F) is injected into themineral oil deposit in process step i), is at least 5° C. above T_(D),preferably at least 15° C., more preferably at least 20° C. andespecially at least 25° C. above T_(D). It is also possible to use theformulation (F) with higher temperatures T_(D). The temperature T_(F),however, is preferably below the boiling point of the formulation (F)under the pressure conditions in the mineral oil deposit. The finalviscosity of the formulation (F) in the deposit depends on theconcentration of the formulation (F) and on the deposit temperature. Thefinal viscosity of the formulation (F) is understood to mean theviscosity of the formulation (F) under deposit conditions (possiblyafter cooling). The greater the difference between T_(F) and T_(D), thedeeper the formulation (F) penetrates into the deposit (for a givenT_(D)). The effect of temperature on the viscosity is shown in FIG. 3.

The temperature of the formulation (F) used depends on the deposittemperature T_(D). In order to satisfy the above temperature conditions,it may be necessary to heat the formulation (F) prior to injection. Thiscan be effected by means of suitable heating elements which may bearranged above ground or within the injection well. The heating of theformulation (F) lowers the viscosity of the formulation (F). Theformulation (F) can penetrate far into the mineral oil deposit as aresult and fill particularly zones of high permeability therein. Afterdeep penetration in the deposit, the formulation (F) cools down and theviscosity of the formulation (F) rises. This also increases theefficiency of the profile modification and the level of oil recovery.

The aims of heating the formulation (F) prior to injection are asfollows:

-   -   deep injection of the formulation (F) into the deposit,    -   injection of heat into the deposit,    -   facilitation of the pumping of the formulation (F).

When the formulation (F) is used as a flooding composition, for examplein the case of development of the deposits with relatively homogeneouspermeability, the optimal concentration of the formulation (F) isdefined according to formula (A), and the formulation (F) is injectedinto the deposit without preheating.

Process Step ii)

In process step ii), the formulation (F) used as a flooding compositionis cooled in the mineral oil deposit. This is preferably effected as aresult of the formulation (F) releasing heat to the surrounding rockformations, the formation water, and possibly the mineral oil.

In a preferred embodiment, the formulation (F) in process step ii) iscooled to such an extent that T_(F) is not more than 10° C. above T_(D).As described above, the viscosity of the formulation (F) increases as aresult of the cooling, as a result of which the mobility of theformulation (F) decreases and highly permeable zones are blocked.

Prior to the performance of process step iii), a further composition forblocking of high-permeability zones can be injected into the mineral oildeposit. This further composition for blocking of high-permeabilityzones is different than the formulation (F) in process steps i) and ii).The injection of the further composition for blocking ofhigh-permeability zones may precede or follow the cooling of theformulation (F).

Suitable further compositions for blocking of high-permeability zonesare formulations (F1) which have a high viscosity under the conditionsin the mineral oil deposit. The further composition for blocking ofhigh-permeability zones preferably forms a gel bank in the mineral oildeposit.

The further composition for blocking of high-permeability zones thusdelimits the formulation (F) injected in process step i). The injectionof a further flooding composition in process step iii) thus preventssubsequent dilution of the formulation (F) for example by waterflooding. This delimits the formulation (F) from the further floodingcomposition.

As a further composition for blocking of high-permeability zones,particular preference is given to formulations (F1) comprising 10 to 40%by weight of crude glycerol (CG), 0.1 to 40% by weight of celluloseether and 2 to 40% by weight of urea, where the percentages by weightare each based on the total weight of the formulation (F1). Under theaction of the deposit temperature, the formulations (F1) form gelshaving viscosity well above the viscosity of the crude glycerol (CG).

As a further composition for blocking of high-permeability zones indeposits having temperatures below 60° C., it is also possible to useknown inorganic aqueous mixtures based on urea, aluminum hydrochlorideand urotropin.

The formulation (F1) forms a gel under the conditions in the mineral oildeposit.

The ending of process step ii) and injection of the formulation (F1) maybe followed by a wait for one to three days. This is advantageous inorder to promote gel formation in formulation (F1).

Process Step iii)

In process step iii), one or more further flooding compositions areinjected into the mineral oil deposit and the production of mineral oilthrough at least one production well is continued. The further floodingcompositions used may, for example, be nitrogen, carbon dioxide, water,and water comprising the customary additives known to those skilled inthe art, such as thickeners and surfactants, preferably water or watercomprising additive.

The “further flooding composition” may be a conventional floodingcomposition which is used predominantly for displacement of the mineraloil (water flooding, polymer flooding, crude glycerol flooding). Inorder to enhance the yield, the mobility of the formulation (F) which isused in step i) should be less under deposit conditions (final mobility)than the mobility of the mineral oil, and less than the mobility of thefurther flooding composition which is used in step iii). The mobility ofthe further flooding composition in step iii) should be less than orequal to the mobility of the mineral oil in the deposit. This enablesefficient displacement of the mineral oil and minimal disruption of thedeposit zones filled with formulation (F) from i). The mobility of theformulation (F) from i) is controlled by the crude glycerolconcentration and the salt content, and the mobility of the formulation(F) from iii) is controlled, for example, by the concentration of thecorresponding thickener. The dependence of the viscosity (mobility) oncrude glycerol concentration studied is shown in FIG. 3.

The present invention thus also provides a process wherein the mobilityof the formulation (F) used in process step i) under deposit conditions(final mobility) is less than the mobility of the mineral oil and lessthan the mobility of the further flooding composition from process stepiii), the mobility of the further flooding composition from process stepiii) being less than or equal to the mobility of the mineral oil.

The term “mineral oil” in this context does not of course meansingle-phase oil, but means the customary emulsions which comprise oiland formation water and are produced from mineral oil deposits.

The injection of the further flooding composition results in formation,in the region between the injection well and production well, of a zonein which the mineral oil is displaced.

The oil production in process step iii) can be performed by customarymethods, for example by injection of one or more further floodingcompositions through at least one injection well into the mineral oildeposit, and mineral oil is withdrawn from the at least one productionwell.

As a further flooding composition, preference is given to using aformulation (F) having a lower crude glycerol concentration (CG) thanthe formulation (F) used in step i). The present invention thereforealso provides a process in which the further flooding composition usedin step iii) is a formulation (F) having a lower crude glycerolconcentration (CG) than the formulation (F) used in step i).

The formulation (F) used in step iii) preferably comprises at least 10%by weight less crude glycerol (CG) than the formulation (F) used in stepi).

The at least one injection well through which the further floodingcomposition is injected in process step iii) may be the injection wellalready used for injection of the formulation (F) in step i). It is alsopossible to inject the further flooding composition in process step iii)through another suitable injection well.

The mineral oil production can of course also be continued by means ofother methods known to those skilled in the art. For example, thefurther flooding composition used may also be aqueous solutions ofsilicate-containing substances or thickening polymers (tertiaryproduction). These may be synthetic polymers, for example polyacrylamideor acrylamide-comprising polymers. In addition, it is also possible touse biopolymers, for example polysaccharides.

It is also possible, after process step iii), to perform process stepsi), ii) and iii) once again. This can be effected at regular intervals,for example once per year. In general, the process according to theinvention is repeated when a water breakthrough is registered in mineraloil production in process step iii) from the production well. Moreparticularly, the process is repeated when critical watering-out ofproduction is attained in mineral oil production in process step iii).This is the case typically when watering-out of production is above 70to 90% by weight. This means that a mixture comprising 70 to 90% byweight of deposit water, based on the total weight of the mixturewithdrawn from the production well, is withdrawn from the productionwell.

Advantages

The process according to the invention for mineral oil production hasthe advantages which follow. The components present in formulation (F)are biodegradable and ecologically very substantially safe. The processaccording to the invention for production of mineral oil enableseffective displacement of the mineral oil and modification of theflooding profile through the possible blockage of permeable regions andchannels in the mineral oil deposit, as a result of which rapid waterbreakthrough is prevented. This is also possible at a relatively largedistance from the injection well. The process according to the inventionis additionally inexpensive, especially through the use of crudeglycerol (CG), and allows efficient profile modification even in mineraloil deposits with relatively low temperatures.

The invention is illustrated in detail by the working examples andfigures which follow.

FIG. 1: Dependence of the density of a formulation (F) comprising waterand glycerol on the glycerol concentration

FIG. 2: Dependence of the boiling temperature of a formulation (F)comprising water and glycerol on the glycerol concentration

FIG. 3: Dependence of the viscosity of a formulation (F) comprisingwater and glycerol on the glycerol concentration

FIG. 4: Scheme of a mineral oil deposit section prior to commencement ofthe process according to the invention

FIG. 5: Scheme of a mineral oil deposit section after performance ofprocess step i)

FIG. 6: Scheme of a mineral oil deposit section after cooling of theformulation (F) (process step ii))

FIG. 7: Scheme of a mineral oil deposit section after injection of thefurther composition for blocking of high-permeability zones(formulations (F1))

In FIGS. 4 to 7, the reference numerals are defined as follows:

1 Injection well

2, 3, 4 Production wells

5 Zone of high permeability (washed-out zone)

6 Near zone filled with formulation (F) prior to cooling

7 Zone filled with formulation (F) after cooling

8 Gel bank

FIG. 1 shows the dependence of the density (at 20° C.) of theformulation (F) comprising glycerol and water on the glycerol content.Plotted on the ordinate (Y axis) is the density (D) in g/cm³. Plotted onthe abscissa (X axis) is the glycerol concentration (C_(Gly)) in % byweight.

FIG. 2 shows the dependence of the boiling temperature of theformulation (F) comprising glycerol and water on the glycerol content atstandard pressure. Plotted on the ordinate (Y axis) is the boilingtemperature (T_(S)) in ° C. Plotted on the abscissa (X axis) is theglycerol concentration (C_(Gly)) in % by weight.

FIG. 3 shows the dependence of the viscosity (at different temperatures)of the formulation (F) comprising glycerol and water on the glycerolcontent. Plotted on the ordinate (Y axis) is the viscosity (Visc) inmPa*s. Plotted on the abscissa (X axis) is the glycerol concentration(C_(Gly)) in % by weight.

FIG. 4 shows a mineral oil deposit, after flooding for several years,which has an inhomogeneous permeability. The region 5 represents a zoneof high permeability between the injection well 1 and the productionwell 4. Hydrodynamic communication between wells 1 and 4 is very good.Outside zone 5, there are regions comprising mineral oil (calledstagnant oil) in the deposit. In zone 5, a deposit temperature of 20° C.is predicted. A formulation (F) comprising 85% by weight of crudeglycerol (CG) and 15% by weight of water is injected through injectionwell 1.

The temperature (T_(F)) of the formulation (F) corresponds at first tothe environment/storage temperature above ground and is 15° C. At thistemperature, the formulation (F) has a viscosity of 100 mPa*s. Themineral oil viscosity (under deposit conditions) is 40 mPa*s.

In order to reduce the viscosity of the formulation (F) in a controlledmanner prior to injection into the mineral oil deposit, the formulation(F) is heated above ground to 40° C. This reduces the viscosity of theformulation (F) to 10 mPa*s. Subsequently, the formulation (F) isinjected through injection well 1. The low-viscosity formulation (F)follows the flood paths that the flooding water took previously in thecourse of secondary production. This fills the near zone 6 of theinjection well 1 with the formulation (F) (FIG. 5).

The low viscosity of the formulation (F) allows it to penetraterelatively deep into zone 5. After cooling of the formulation (F) in thedeposit under the action of the low deposit temperature (T_(D)), theviscosity of the formulation (F) in the near zone 6 rises to 70 to 80mPa*s, and the zone 7 forms (see FIG. 6). The formulation (F) forms ahigh hydraulic resistance in zone 7.

Subsequently, process step iii) is performed and a further floodingcomposition (for example water) is injected through the injection well(see FIG. 6). Due to the high hydraulic resistance in zone 7, thefurther flooding composition takes other paths (symbolized by the curvedarrows). As a result, mineral oil outside the high-permeability zone 5is displaced and can be withdrawn through production wells 2 and 3.

FIG. 8 shows a further embodiment. In this case, before or after coolingof the formulation (F) and formation of zone 7, a further floodingcomposition (for example water) is not injected directly. Instead, afurther composition is first injected to block high-permeabilityregions. Since the temperature of the deposits is low, preference isgiven to using the formulation based on urea, aluminum hydrochloride andurotropin.

This formation gelates in the near region of the injection well. Arelatively small portion of this formulation is injected through theinjection well. The formulation forms a high-viscosity gel bank 8 in themineral oil deposit between zone 7 and the injection well. This protectszone 7 from dilution by the further flooding composition (for examplewater) used subsequently. This minimizes the dynamic properties/movementof zone 7 and the dilution of the crude glycerol (CG) in zone 7.

Subsequently, a further flooding composition is injected throughinjection well 1, for example water or thickened water. It is optimalwhen the viscosity of the further flooding composition (post-floodingcomposition) is much less than the final viscosity of the crude glycerol(CG) in zone 7 and is equal to or somewhat higher than the mineral oilviscosity. As a result, mineral oil present outside the highly permeablezone 5 is displaced and can be withdrawn through production wells 2 and3.

It is also possible to inject formulation (F1) into the mineral oildeposit prior to the cooling of the formulation (F).

This example describes an execution variant of the process in thedevelopment of a “mature” deposit with marked inhomogeneity of thepermeability. The main purpose of injecting the formulation (F) (stepi)) into the deposit is the modification of the flood profile.

Another important field of use of the process is the use of theformulation (F) predominantly for the displacement of the mineral oil.In this case, the deposit is flooded with the formulation (F) (theprocess is then limited to step i)). For this purpose, conventionaltechnologies are used.

1.-12. (canceled)
 13. A process for tertiary production of mineral oilfrom underground mineral oil deposits having a deposit temperatureT_(D), into which at least one injection well and at least oneproduction well have been sunk, comprising at least the followingprocess steps: i) injecting a flooding composition through at least oneinjection well into the mineral oil deposit, using, as the floodingcomposition, a formulation (F) having a temperature T_(F) higher thanthe temperature T_(D), ii) cooling the flooding composition from step i)in the mineral oil deposit and iii) injecting a further floodingcomposition through at least one injection well into the mineral oildeposit and withdrawing mineral oil through at least one productionwell, wherein the formulation (F) comprises crude glycerol (CG) havingthe following composition: 80 to 90% by weight of glycerol, 10 to 20% byweight of water, 0 to 10% by weight of inorganic salts and 0 to 1% byweight of organic compounds, where the percentages by weight are eachbased on the total weight of the crude glycerol (CG).
 14. The processaccording to claim 13, wherein the formulation (F) comprises at least10% by weight of crude glycerol (CG), based on the total weight of theformulation (F).
 15. The process according to claim 13, wherein theformulation (F) comprises 10 to 99% by weight of crude glycerol (CG), 1to 90% by weight of water and 0 to 20% by weight of at least oneinorganic salt, where the percentages by weight are each based on thetotal weight of the formulation (F).
 16. The process according to claim13, wherein the formulation (F) comprises at least 80% by weight ofcrude glycerol (CG), where the percentages by weight are each based onthe total weight of the formulation (F).
 17. The process according toclaim 13, wherein the formulation (F) comprises at least 90% by weightof crude glycerol (CG), where the percentage by weight is based on thetotal weight of the formulation (F).
 18. The process according to claim13, wherein the formulation (F) comprises at least 99% by weight ofcrude glycerol (CG), where the percentage by weight is based on thetotal weight of the formulation (F).
 19. The process according to claim13, wherein the mobility of the formulation (F) used in process step i)under deposit conditions (final mobility) is less than the mobility ofthe mineral oil and less than the mobility of the further floodingcomposition from process step iii), the mobility of the further floodingcomposition from process step iii) being less than or equal to themobility of the mineral oil.
 20. The process according to claim 13,wherein the deposit temperature TD is below 60° C.
 21. The processaccording of claim 13, wherein the flooding composition in step ii) iscooled to a temperature not more than 10° C. above the deposittemperature TD.
 22. The process according claim 13, wherein the deposittemperature TD is in the range from 0 to 40° C.
 23. The processaccording of claim 13, wherein the formulation (F) used as the floodingcomposition in step i) is heated to establish the temperature TF priorto injection into the mineral oil deposit.
 24. The process according ofclaim 13, wherein step i) or step ii) is followed by injection of afurther composition into the mineral oil deposit for blocking of highlypermeable regions.
 25. The process according of claim 13, wherein thefurther flooding composition used in step iii) is a formulation (F)having a lower crude glycerol concentration (CG) than the formulation(F) used in step i).
 26. The process according to claim 24, wherein thefurther composition used for blocking of highly permeable zones is aformulation comprising 10 to 40% by weight of crude glycerol (CG), 0.1to 40% by weight of cellulose ether and 2 to 40% by weight of urea,where the percentages by weight are each based on the total weight ofthe formulation.